La Fortaleza (The Fortress) is the official residence of the governors of Puerto Rico. La Fortaleza was the first fortification built in San Juan harbour. The original tower, now called Torre del Homenaje, or "tower of homage," still stands; its name derives from an island tradition in which the resident governor climbs to the top of the tower to pledge a solemn oath of loyalty and courage during dangerous times.

The cathedral is one of the oldest buildings in San Juan, and the oldest cathedral in the United States, and is the second oldest cathedral in the Americas. The building of the San Juan Cathedral was part of the establishment and spread of Catholicism on the island. The cathedral contains the tomb of the Spanish explorer and settlement founder Juan Ponce de León.

Also known as the (Old Entrance of San Juan), the gate was built in 1635, this gate was the main entry into the walled city during its Spanish colonial era. It is 16 feet tall and 20 feet thick and leads you to the romantic Paseo La Princesa.

La Rogativa, one of the most beautiful sculptures in Old San Juan, takes centre stage at the plaza. The sculpture was made out of bronze. Rogativa means “The Procession”, which tells the legend about a Catholic Bishop and his companions who made a procession in faith holding crosses, torches, and chanting during an invasion by the British on the city in 1797.

Built in 1521, it was the residence for Juan Ponce de León and his family. Now serves as a museum.

The Bastion was built next to Castillo San Felipe del Morro and it was meant as an added defence to the fort. In the 1800s, this bastion served as barracks for the soldiers.

Built in 1854 and used until 1898 by the Spaniards. The Cuartel was built as barracks for the Spanish Infantry. It was made to house 1000 soldiers and their families. After the 1898 invasion by the US Army, the US infantry occupied the Cuartel de Ballajá until 1936. During the Second World War, this structure became a hospital.

El Morro was the second fortress built in Old San Juan to protect the city from attack and invaders. It was built in a strategic position where it could attack ships with cannons from different angles. During the First and Second World Wars, El Morro was used by the US Army and today it serves as a National Park.